Differential temperature compensator for radial seals



y 7, 1963 w. H. RAYBURN 3,088,518

. DIFFERENTIAL TEMPERATURE COMPENSATOR FOR RADIAL SEALS Filed Oct. 25,1960 H07 END COLD 5N0 5:6 ,52 izflmfl'l g,

7 AW! P 3 99 a6 2 a i; \o !"l"!" 30 M a T.

3,088,518 Patented May 7, 1963 The present invention relates generallyto heat exchange apparatus, and particularly it relates to an improvedradial sealing arrangement for use between a rotor and adjacent endplates of a housing enclosing the rotor of a rotary regenerative heatexchanger.

In rotary regenerative heat exchange apparatus of the type hereindefined, a cylindrical rotor has compartments carrying heat transfermaterial which are first exposed to heating gases and then as the rotorturns about its axis, the compartments of heat transfer material areexposed to air or other fluid to be heated passing through an airpassage where the heated heat transfer material imparts absorbed heat tothe air. The rotor is surrounded by a housing having end or sectorplates formed with openings that provide for the flow of heating gasesand air therethrough. To prevent mingling of the two fluids, radialpartitions that form the rotor compartments are provided with radialsealing members that wipe against imperforate portions of the sectorplate.

Radial sealing members are usually secured to the end edges of theradial partitions in such a manner that they twist and bend inaccordance with the temperature gradient of the radial partitions towhich they are attached. Various arrangements for mounting the radialsealing members independent from the radial partitions and actuatingthem into a sealing relationship with the adjacent face of an end platehave been tried and in many instances found to be satisfactory undercertain conditions. Among such arrangements that have been tried arethermal actuating means that move the sealing means in re sponse to anincrease or decrease in the average temperature of a thermallyresponsive element. A serious objection to the use of such anarrangement relates to the fact that such means is not dependent on thedegree of distortion but only on the intensity of the temperature. Thussuch an actuating means would provide a continuous and sometimesexcessive actuation so long as the temperature would continue to lie orrise above a given reference point.

Under certain conditions of operation as during a start up or during acleaning operation when the flow of air or other cool fluid through theheat exchanger has been substantially curtailed, the temperature of aheat exchanger will rise substantially and assume a nearly constanttmperature throughout such that thermal actuating means of the usualtype will continue to expand and force the sealing means against the endplate to provide excessive wear and possible binding of the relativelymoving members.

Such wear or binding of the sealing members may necessitate their repairor replacement even before they have been placed in active service. Thepresent invention therefore has as one of its principal objects thethermal actuation of a sealing unit only when subjected to normaloperating conditions that impress a temperature differential across therotor of a heat exchanger.

A further object of this invention is to provide a device formaintaining a fixed position at the outboard end of a radial seal in arotary regenerative heat exchanger where a diaphragm thereof is turneddown as a result of a temperature gradient caused by the passage of aheating fluid and a fluid to be heated therethrough.

When fluid flow is directed through a heat exchanger the diaphragmsdeflect in accordance with the formula:

ocATX where:

a=coeflicient of expansion of the metal,

AT=temperature differential across the heat exchanger in F.

X :radial length of diahpragm in inches, and

Y=axial depth of diaphragm in inches.

Thus any system designed to compensate precisely for normal thermaldeflection of a rotor must be actuated by a differential of temperatureacross such structure rather than merely by a variation in temperatureat a particular point.

Therefore, the present invention is directed to an improved sealingarrangement that compensates directly for a differential in temperatureacross the rotor of a rotary regenerative heat exchange apparatus.

The invention will be more clearly understood upon consideration of thefollowing detailed description of an illustrative embodiment thereofwhen read in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional elevation in diagrammatic form showing a rotaryregenerative heat exchanger involving the invention.

FIGURE 2 is an enlarged fragmentary view in section showing therelationship of the various elements that comprise the invention.

In the drawings, the numeral 10 designates a cylindrical shell of arotor divided into a series of sector shaped compartments by radialpartitions or diaphragms 11 connecting it with a rotor post '12 which isturned slowly about its axis by a motor and. reducing gear arrangementillustrated at 13. The rotor compartments are packed with regenerativeheat exchange material in the form of perforate material or spacedmetallic plates which first absorb heat from hot gases entering the heatexchanger through a duct 15 from a boiler furnace to be discharged afterpassing over the heat exchange material through an outlet duct 16 towhich an induced draft fan (not illustrated) is usually connected. Asthe rotor turns slowly about its axis the heated plates are moved intothe stream of air admitted through duct 17. After passing over platesand absorbing heat therefrom, the stream of heated air is conveyed to aboiler furnace or other place of use through a duct 18.

A housing 20 enclosing the rotor Ill is provided at either end oppositethe rotor with end or sector plates 21 which are apertured at 22 and 23to admit and discharge streams of hot gas and cool air flowing throughthe rotor. In order that streams of gas and air do not bypass the rotorby flowing through the annular clearance space 24 between the rotorshell 10 and rotor housing 20, it is customary to providecircumferential seals indicated at 25 on the end edge of rotor shell 10to bear against confronting parts of sector plates 21 and seal oif space24 from each end of the rotor. Radial sealing means 30 are also providedat the end edges of the radial partitions to bridge the space betweenthe partitions and the confronting imperforate face of the adjacent endplate.

The radial sealing means at one or both ends of the rotor are supportedindependent of the radial partitions in order that thermal deformationor turn down of the partitions due to a temperature gradient across theheat absorbent element and adjacent partitions will not be transmittedto the sealing members to alter their predetermined sealingrelationship.

In this invention, radial sealing means of this general type are pivotedat 32, preferably adjacent the rotor post, while the remote end thereofis axially movable toward or away from the confronting face of theadjacent end plate 21. Pivoted sealing means of this type arenecessarily provided only at What is commonly termed the hot end of therotor inasmuch as during operation uneven thermal expansion of the rotorforces the rotor to turn-down or move away from the end plate at the hotend of the rotor while at the opposite or cold end of the rotor thereverse is true and the rotor including sealing means attached theretois moved toward the confronting face of the end plate.

Accordingly, the seal actuating means comprises essentially two radiallyextending expansion bars 34 and 35 that are securely attached at theirinner ends to axially remote parts of the diaphragm 11 in order thattheir outboard ends may be entirely free to move radially relative tothe adjacent diaphragm. A slot 36 in one or both expansion barsembracing a pin 39 on the diaphragm adjacent thereto permitsunencumbered radial expansion of the expansion bar while itsimultaneously provides an axial support for their outboard ends. Sincethermal distortion or turn-down of a diaphragm occurs primarily at itsdistal end, the slot 36 and supporting pin 39 are preferably positionedsubstantially midway between inner and outer extremities of thediaphragm to provide a substantial support for the sealing means that issubject only to a fractional amount of turn-down evident at its outerend. The expansion bars are preferably comprised of a material such asstainless steel having a high coefiicient of expansion in order that asmall change in temperature will provide substantial radial movement attheir outboard ends. Both expansion members are however formed of thesame material and of the same length to provide equal expansion whensubjected to a common temperature and different degrees of expansionwhen subjected to different temperatures.

The outboard ends of the expansion bars 34- and 35 are pivotallyattached at 42 and 44 to an axial connecting bar 46 and includes acantilever portion 48 extending axially to a point laterally adjacentthe outboard end of the pivoted radial seal. The connecting bar 46 isformed from the same material as the diaphragm adjacent thereto in orderthat the connecting bar and a laterally adjacent segment of thediaphragm will expand or contract in unison when subjected to theprevailing temperature.

A driver cam 52 having a radial slot 54 formed therein is secured to thecantilever end 48 of the connecting bar 46 and arranged to slidablyembrace a pin 56 protruding from the side of the radial seal. The lengthof the driver cam 52 and its slot 54 is determined by the size, materialand operating temperatures of the heat exchanger whose radial seal it isdesigned to actuate, since rotation of the driver cam 52 about pivot 42should provide a vertical component of force to pin 56 that neutralizesthe turn-down of the rotor occurring at pin 39.

Under conditions that obtain a constant temperature at both ends of therotor the radial expansion bars 34 and 35 will be of equal length andthe connecting bar 46 linked normal thereto will lie in a substantiallyvertical position. With the expansion bars thus positioned the drivercam 52 will lie in its original horizontal position 4 and the pivotedradial seal 30 will continue to lie in its original non-actuated orneutral position.

When normal flow of a heating fluid and a fluid to be heated through theheat exchanger is initiated, the temperature gradient across the rotorwill increase with the greatest increase of temperature occurring at thehot end adjacent expansion bar 34. This varying increase of temperatureeffects substantially greater thermal expansion of bar 34 than of bar 35thereby forcing the upper end of connecting bar 46 to slope outward andincline the driver cam 52 upward such that it raises the pin 56 and thepivoted sealing member 30 to which it is attached towards the adjacentend plate to neutralize the downward movement of the diaphragm 11 thatoccurs between the pin 39 and the rotor post as caused by rotorturndown.

Thus operating conditions which normally effect distortion or rotorturn-down and result in excessive leakage of fluid through the clearancespace between the sealing means and the adjacent end plate are utilizedto actuate the sealing means into a preferred sealing relationship withthe adjacent face of the end plate. Moreover, under certain conditionswhere there exists no temperature differential across the rotor therecan be no actuation of the sealing means, and such sealing means are notforced unnecessarily into contact with the adjacent housing members.

While this invention has been described with reference to the embodimentillustrated in the drawing it is evident that numerous changes may bemade in the several elements to provide the desired degree of sealactuation without departing from the spirit of the invention, and it isintended that all matter contained in the above description or shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

What I claim is:

1. A regenerative heat exchanger having a rotor including a cylindricalrotor shell joined to a rotor post by radial partitions to formsectorial compartments that carry a mass of heat transfer material, anda cylindrical housing surrounding the rotor provided at opposite endsthereof with end plates including imperforate portions located betweencircumferentially spaced apertures that direct the flow of heating fluidand fluid to be heated through the regenerative heat transfer materialcarried by the rotor, radial sealing means bridging the space between anend edge of each radial partition and the adjacent end plate to precludefluid flow therebetween, said sealing means including radially extendingleaf members pivotally attached at one end thereof to an axial end edgeof said radial partition, and actuating means at the distal end of saidleaf members lying adjacent the inlet aperture for the heating fluidarranged to move them toward the adjacent end plate in response to thedifferential of temperature that distorts the radial partitions in theopposite direction.

2. Regenerative heat exchange apparatus having a rotor including acylindrical rotor shell joined to a rotor post by radial partitions toform sectorial compartments that carry a mass of heat transfer material,and a cylindrical housing surrounding the rotor and provided at oppositeends thereof with end plates including irnperforate portions locatedbetween circumferentially spaced apertures that direct the flow ofheating fluid and a fluid to be heated through the regenerative heatexchange material carried by the rotor, radial sealing means bridgingthe space between an end edge of each radial partition and the adjacentend plate to preclude fluid flow therebetween, said sealing meansincluding a radially extending leaf member lying adjacent and pivotallyattached at one end to the radial partition, actuating means linked tothe opposite end of said leaf member to bias it toward the end plateinversely as the radial partition moves away therefrom, said actuatingmeans comprising radial expansion bars at axially spaced ends of eachdiaphragm having one end fixed thereto while the distal ends thereof 5 6are free to expand radially in response to a change of having a linkagemeans including a radial slot in the temperature, a linking barpivotally attached to the disdriver cam slidably embracing a pin aflixedto the side of tal ends of said expansion bars, and means responsive tosaid pivoted sealing means. an inclination of said linking bar adaptedto provide a component of force moving the sealing means into seal- 5References C d 1 1 the fil 0f thIS patent ing relationship with theadjacent end plate.

3. A regenerative heat exchanger as defined in claim UNITED STATESPATENTS 2 wherein the means responsive to the inclination of said2,681,203 Boestad et June 15, 1954 l'ki b i d a flixdth toand in ng arcompr ses a river c m a e ere FOREIGN PATENTS lying adjacent the pivotedsealing means.

4. A regenerative heat exhanger as defined in claim 3 10 1,144,668France Oct. 16, 1957

1. A REGENERATIVE HEAT EXCHANGER HAVING A ROTOR INCLUDING A CYLINDRICALROTOR SHELL JOINED TO A ROTOR POST BY RADIAL PARTITIONS TO FORMSECTORIAL COMPARTMENTS THAT CARRY A MASS OF HEAT TRANSFER MATERIAL, ANDA CYLINDRICAL HOUSING SURROUNDING THE ROTOR PORVIDED AT OPPOSITE ENDSTHEREOF WITH END PLATES INCLUDING IMPERFORATE PORTIONS LOCATED BETWEENCIRCUMFERENTIALLY SPACED APERTURES THAT DIRECT THE FLOW OF HEATING FLUIDAND FLUID TO BE HEATED THROUGH THE REGENERATIVE HEAT TRANSFER MATERIALCARRIED BY THE ROTOR, RADIAL SEALING MEANS BRIDGING THE SPACE BETWEEN ANEND EDGE OF EACH RADIAL PARTITION AND THE ADJACENT END PLATE TO PRECLUDEFLUID FLOW THEREBETWEEN, SAID SEALING MEANS INCLUDING RADIALLY EXTENDINGLEAF MEMBERS PIVOTALLY ATTACHED